Quantum Monte Carlo study of the pairing symmetry competition in the Hubbard model

To shed light into the pairing mechanism of possible spin triplet superconductors (TMTSF)(2)X and Sr2RuO4, we study the competition among various spin singlet and triplet pairing channels in the Hubbard model by calculating the pairing interaction vertex using the ground state quantum Monte Carlo technique. We model (TMTSF)(2)X by a quarter-filled quasi-one-dimensional (quasi-1D) Hubbard model, and the gamma band of Sr2RuO4 by a two-dimensional (2D) Hubbard model with a band filling of similar to4/3. For the quasi-1D system, we find that triplet f-wave pairing not only dominates over the triplet p wave in agreement with the spin fluctuation theory, but also looks unexpectedly competitive against d waves. For the 2D system, although the results suggest the presence of an attractive interaction in the triplet pairing channels, the d-wave pairing interaction is found to be larger than those of the triplet channels.